1. Field of the Invention
This invention relates to new spandex compositions comprising poly(tetramethylene-co-ethyleneether) glycols comprising constituent units derived by copolymerizing tetrahydrofuran and ethylene oxide, wherein the portion of the units derived from ethylene oxide is present in the poly(tetramethylene-co-ethyleneether) glycol from about 16 to about 70 mole percent and wherein the spandex filaments are spun at high speed, typically greater than 750 meters per minute.
2. Description of the Related Art
Poly(tetramethylene ether) glycols, also known as polytetrahydrofuran or homopolymers of tetrahydrofuran (THF, oxolane) are well known for their use in soft segments in polyurethaneureas. Poly(tetramethylene ether) glycols impart superior dynamic properties to polyurethaneurea elastomers and fibers. They possess very low glass transition temperatures, but have crystalline melt temperatures above room temperature. Thus, they are waxy solids at ambient temperatures and need to be kept at elevated temperatures to prevent solidification.
Copolymerization with a cyclic ether has been used to reduce the crystallinity of the polytetramethylene ether chains. This lowers the polymer melt temperature of the copolyether glycol and at the same time improves certain dynamic properties of the polyurethaneurea that contains such a copolymer as a soft segment. Among the comonomers used for this purpose is ethylene oxide, which can lower the copolymer melt temperature to below ambient, depending on the comonomer content. Use of poly(tetramethylene-co-ethyleneether) glycols may also improve certain dynamic properties of polyurethaneureas, such as elongation at break and low temperature performance, which is desirable for some end uses.
Poly(tetramethylene-co-ethyleneether) glycols are known in the art. Their preparation is described in U.S. Pat. Nos. 4,139,567 and 4,153,786. Such copolymers can be prepared by any of the known methods of cyclic ether polymerization, such as those described in “Polytetrahydrofuran” by P. Dreyfuss (Gordon & Breach, N.Y. 1982), for example. Such polymerization methods include catalysis by strong proton or Lewis acids, heteropoly acids, and perfluorosulfonic acids or acid resins. In some instances it may be advantageous to use a polymerization promoter, such as a carboxylic acid anhydride, as described in U.S. Pat. No. 4,163,115. In these cases, the primary polymer products are diesters, which then need to be hydrolyzed in a subsequent step to obtain the desired polymeric glycols.
Poly(tetramethylene-co-ethyleneether) glycols offer advantages over poly(tetramethylene ether) glycols in terms of certain specific physical properties. At ethyleneether contents above 20 mole percent, the poly(tetramethylene-co-ethyleneether) glycols are moderately viscous liquids at room temperature and have a lower viscosity than poly(tetramethylene ether) glycols of the same molecular weight at temperatures above the melting point of poly(tetramethylene ether) glycols. Certain physical properties of the polyurethanes or polyurethaneureas prepared from poly(tetramethylene-co-ethyleneether) glycols surpass the properties of those polyurethanes or polyurethaneureas prepared from poly(tetramethylene ether) glycols.
Spandex based on poly(tetramethylene-co-ethyleneether) glycols is also known in the art. For example, U.S. Pat. No. 4,224,432 to Pechhold et al. discloses the use of poly(tetramethylene-co-ethyleneether) glycols with low cyclic ether content to prepare spandex and other polyurethaneureas. Pechhold teaches that ethyleneether levels above 30 percent are preferred. Pechhold does not teach the use of coextenders, though it discloses that mixtures of amines may be used.
U.S. Pat. No. 4,658,065 to Aoshima et al. discloses the preparation of several THF copolyethers via the reaction of THF and polyhydric alcohols using heteropolyacid catalysts. Aoshima also discloses that copolymerizable cyclic ethers, such as ethylene oxide, may be included with the THF in the polymerization process. Aoshima discloses that the copolyether glycols may be used to prepare spandex, but contains no examples of spandex from poly(tetramethylene-co-ethyleneether) glycols.
U.S. Pat. No. 3,425,999 to Axelrood et al. discloses the preparation of polyether urethaneureas from poly(tetramethylene-co-ethyleneether) glycols for use in oil resistance and good low temperature performance. The poly(tetramethylene-co-ethyleneether) glycols have ethyleneether content ranging from 20 to 60 percent by weight (equivalent to 29 to 71 mole percent). Axelrood does not disclose the use of these urethaneureas in spandex. Axelrood discloses that “the chain extenders most useful in this invention are diamines selected from the group consisting of primary and secondary diamines and mixtures thereof.” Axelrood further discloses that “the preferred diamines are hindered diamines, such as dichlorobenzidine and methylene bis(2-chloroaniline).” Use of ethylene diamine is not disclosed.
U.S. Pat. No. 6,639,041 to Nishikawa et al. discloses fibers having good elasticity at low temperature that contain polyurethaneureas prepared from polyols containing copolyethers of THF, ethylene oxide, and/or propylene oxide, diisocyanates, and diamines and polymers solvated in organic solvents. Nishikawa teaches that these compositions have improved low temperature performance over standard homopolymer spandexes. Nishikawa also teaches that “above about 37 mole % ethyleneether content in the copolyether glycol, unload power at low elongations is unacceptably low, elongation-at-break declines, and set rises, though very slightly.” The examples in Nishikawa show that as the mole percent of ethylene ether moiety in the copolyether increases from 22 to 31 to 37 mole percent, the elongation at break rises, but upon increasing to 50 mole percent, the elongation at break then drops. In contrast, the spandex of the present invention exhibits a trend of increasing elongation at break as mole percent of ethylene ether moiety in the copolyether increases from 27 to 49 mole percent. All of the examples in this patent were spun at 650 meters/min. or less.
Spinning spandex faster to make more fiber in a given amount of time and thus reduce manufacturing cost is obvious to any fiber producer, but the spinning speed is limited by the negative effect on some of the fiber properties. It is well known to those skilled in the art that increasing the spinning speed of a spandex composition will reduce its elongation and raise its load power compared to the same spandex spun at a lower speed. Thus, the faster a spandex fiber is spun the more the elongation is reduced and the load power is increased, resulting in reduced draftability of the fiber. Reduced draftability results in requiring more spandex to be used in garment construction and thus increases the cost of garment manufacture. Therefore, it is common practice to slow spinning speeds in order to increase the elongation and reduce the load power of a spandex in order to increase its draftability in circular knitting and other spandex processing operations.
One approach to increasing productivity based on spinning techniques is disclosed in U.S. Pat. No. 6,916,896 to Selling et al. Selling describes using polyurethaneurea compositions with mixed diisocyanates to increase polymer solution solubility so that a higher solids polyurethaneurea solution may be spun. Even though higher spinning speeds are not used, productivity as measured by weight of spandex yarn produced in a given time is increased. The polyurethaneureas of the present invention also have high solution solubility without mixed diisocyanates and have much higher productivities than Selling.
Yet another approach to increased productivity through optimal spinning conditions is disclosed in JP2002-155421A “Dry-Spinning Process.” JP2002-155421A discloses a method for increasing productivity in dry spinning polyurethanes. This method is based on adjusting cell spinning conditions to avoid the upward flow of drying gas in the spinning cell and avoiding threadline lateral instability. The two examples of JP2002-155421A both employ poly(tetramethylene ether) glycol-based spandex. JP2002-155421A does not disclose the types of spandexes suitable for the invention. The process of the present invention appears to be independent of spinning cell conditions beyond those necessary to produce a suitably dry fiber (e.g., 0 to 0.5 percent dimethylacetamide solvent remaining in the fiber). In addition, no additives are necessary.
The applicants have observed that spandex with poly(tetramethylene-co-ethyleneether) glycols having from about 16 to about 70 mole percent, for example from greater than about 37 to about 70 mole percent, of its constituent units derived from ethylene oxide as the soft segment base material and which is also spun at high speeds, i.e., greater than 750 meters/min., provides improved physical properties over other spandexes spun at similarly high speeds. Spandex based on other copolyether glycols such as poly(tetramethylene-co-2-methyltetramethyleneether) or polyester glycols such as the copolyester of ethylene glycol, 1,4-butylene glycol and adipic acid also have low load power. However, these spandexes also generally have low tenacity or low elongation or both that limits their ability to be spun at speeds in excess of 1000 meters/min.
The poly(tetramethylene-co-ethyleneether) glycol-based spandex of the present invention possesses the combination of low load power, high elongation, and adequate tenacity that allows it to be spun at speeds in excess of 1300 meters/min., producing a fiber with excellent draftability in circular knitting operations. In addition, the spandex of the present invention shows a desirable reduction in shrinkage in hot wet processing when it is spun at windup speeds greater than 1000 meters/min.